Seismic early warning is being recognized as a methodology which offers the biggest potential for real time seismic risk mitigation, particularly in towns and industrial areas. In order to be effectively applied it requires close cooperation between seismologists, communication experts and seismic engineers. The added value of this book is to offer an overview of frontier problems related to all aspects of the seismic early warning chain, from basic seismological issues to engineering problems and system reliability. Early warning seismic networks also provide near real time shake maps for damage estimation and emergency management immediately after an event. The state of the major early warning systems in operation and in the course of development (e.g. those operated in Japan, Taiwan, Rumania, Turkey and those being implemented in California and Southern Italy) is also presented. It is the first time that all these aspects are specifically focused upon within a single book. It will constitute a reference not only for researchers and students, but for all institutions which are willing to face the development and/or implementation of this methodology, including International organizations (UNDP, European Civil Protection, European Commision) National Civil Defence organizations, industry and town-planners.